Method of operating an internal combustion engine and motor fuel therefor



United States Patent METHOD'OF OPERATING AN INTERNAL COMBUSTION ENGINE AND MOTOR FUEL THEREFOR George W. Eckert, Wappingers Falls, N.Y., assignor to Texaco Inc., New York, N.Y., a corporation of Delaware 1 No Drawing. Filed Apr. 11, 1967, Ser. No. 629,897

12 Claims. (Cl. 44-71) ABSTRACT OF THE DISCLOSURE There is disclosed a method for operating an internal combustion gasoline engine and a novel motor fuel composition for said process comprising a mixture of hydrocarbons in the gasoline boiling range and a substituted urea.

The present invention relates to a method for operating an internal combustion engine which gives a substantial improvement in fuel economy. This invention also relates to a novel fuel composition for use in the process comprising a mixture of hydrocarbons in the gasoline boiling range containing a viscosity thickening amount of an oil-soluble substituted urea.

Methods for improving fuel economy in the operation of gasoline-powered automobiles by altering the physical properties of the fuel have been described before. For example, the viscosity of gasoline can be increased so that effective engine operation is obtained using leaner fuel-air ratios under normal driving conditions. Not only is the fuel consumption of the gasoline-burning automobile substantially reduced but the improvement is realized without any mechanical change in the carburetor or other parts of the engine. Such a method is disclosed in US. Patent 3,164,138 which issued on Jan. 5,

The present invention is based on the discovery that substituted ureas are effective for modifying the fluid properties of gasoline. More specifically, an economical engine operation is achieved by burning a gasoline in which the viscosity has been substantially increased due to the addition of a substituted urea to the fuel composition. The viscosity increase in the gasoline gives a lower rate of gasoline flow through the carburetor under ordinary level road driving conditions without appreciably altering the specific volume of air entering the engine, thereby producing a leaner fuel-air combustion mixture. Besides improving fuel efficiency the leaner mixture operation results in a reduction of undesirable exhaust emissions from the vehicle.

; In accordance Withthe method of this invention, a spark-ignited internal combustion engine is operated by burning a motor fuel composition containing a viscosity modifying oil-soluble substituted urea formed from the reaction of a specific type of amine with toluene diisocyanate. The motor fuel of the invention comprises a mixture of hydrocarbons in the gasoline boiling range containing .an amount of the substituted urea effective to substantially increase the viscosity of the motor fuel over the viscosity of the hydrocarbon mixture. More particularly, the amount of the oil-soluble substituted urea employed in the motor fuel is effective to increase the viscosity of the motor fuel by at least and up to about 200% over the viscosity of the hydrocarbon mixture under the conditions selected for the viscosity determinations. The viscosity of the fuel can be measured by any of the standard methods for viscosity determinations of liquids provided that conditions are selected to minimize discrepancies which could arise from the evaporation of highly volatile components of the gaso- 3,403,013 Patented Sept. 24, 1968.

line. The viscosity of the gasolines described herein was measured by the Kinematic Viscosity Procedure (units in centistokes) at 77 F.

The oil-soluble substituted ureas which have been found effective for thickening the fuels of the invention are represented by the following formula:'

in which R and R are each alkyl radicals having from 1 to 18 carbon atoms and the sum of the carbon atoms in all the R and R radicals is at least 12 and preferably at least 18. The foregoing compounds are prepared by reacting a secondary alkyl primary amine with a toluene diisocyanate having the formula:

secondary carbon atom. These amines correspond to the in which R and R are alkyl radicals having from 1 to 18 carbon atoms with the sum of the carbon atoms in R and R being at least 6. Secondary alkyl primary amines are commercially available generally as mixtures of amines having alkyl radicals in a narrow molecular weight range. An n-alkyl primary beta amine having an average molecular weight of about and an average of about 11 carbon atoms is marketed as Armeen L-9. Armeen L-11 is an n-alkyl primary beta amine having an average molecular weight of 20S and an average of 13 carbon atoms. These are described on page 40 of Chemical Engineering News, dated J an. 11, 1965. Other effective secondary alkyl primary amines are Z-amino octane, 3-amino octane, 4-amino octane, 3-amino decane and 2-amino dodecane. The preferred amines are those in which the sum of the carbon atoms in -R and R is at least 9.

The nature of the amine component of the substituted urea is critical to the process and motor fuel of this invention. Many amines which react with toluene diisocyanate to form substituted ureas are insoluble in or otherwise ineffective for increasing the viscosity of gasoline. These amines are clearly outside of the scope of the present invention. Examples of amines which do not form effective substituted ureas when reacted with toluene diisocyanate include monoamines, such as aniline, benzylamines, cyclohexylamine, ethoxyethylamine, stearylamine and p-toluidine and diamines, such as N-2-undecyl-1,3- propane diamine.

It is essential that the oil-soluble substituted urea of the invention substantially increase the viscosity of the motor fuel composition over the viscosity of the hydrocarbon mixture or base fuel. A viscosity increase of at least 10% gine operating at 30 miles per hour under level road conin the motor fuel measured as the kinematic viscosity in ditions showed that the fuel of increased viscosity produced centistokes is critical to provide a distinct improvement in operating economies of 4.5%. Similarly, a premium motor fuel economy. This determination may be made at any fuel which has had its viscosity increased by 24.6% when convenient temperature, such as at 77 F. in the present 5 tested in a General Motors Research Engine at-:30 miles invention, or at F. as in the abovenoted patent. Actuper hour level road conditions showed that the fuel/ air ally, the viscosity of a gasoline can be increased by several ratio was reduced by about 17% and that the fuel economy hundred percent or more by adding an oil-soluble viscosity was improved by about 7.2%. modifying substituted urea. However, a viscosity increase Gasolines which have had their viscosities increased in in the range of at least 10 to about 200% is the critical 10 the order of 50% according to this invention have shown range to produce the desired operating economies. Viscossubstantial improvements in fuel economy ranging from ity increases from about 20 to 100% are preferred with to or more over the base fuel depending on the load optimum results being realized with viscosity increases of conditions employed. Similarly, gasolines that have had from 40 to 100%. The foregoing viscosity increases are their viscosity increased in the order of 100% or more generally realized by employing the oil-soluble substituted have been, observed to provide fuel economies substanurea of the invention in an amount from about 0.005 to tially in excess of 0.5 weight percent based on said gasoline. Preferred The effect of the substituted ureas of this invention was amounts of the substituted urea in gasoline range from determined in the following test. The base fuel employed about 0.01 to 0.2 weight percent. Excessively high vis was a premium gasoline containing 3.09 cc./ gallon of cosity increases, that is, a viscosity increase substantially 20 tetraethyl lead fluid mixture. This gasoline had a Reover 300% generally, produce a fuel having unsatisfactory search Octane No. of 101.2, a boiling range from 87 F. flow properties. Such viscosity increases in a fuel sufficient to 368 F., a kinematic viscosity in centistokes at 77 F. to reduce the fuel/ air ratio to less than 0.06 will also genof 0.557 and consisted of 31.5 percent aromatics, 10.5 perer-ally result in misfiring and loss of power. cent olefins and 58 percent saturates as determined by A base fuel or gasoline without the viscosity modifying conventional FIA analysis. The table below gives the conoil-soluble substituted urea of the invention will generally centration of the substituted urea additive in the gasoline have a kinematic viscosity in centistokes at 77 F. in the in weight percent. Since all of the additives were prepared range of 0.500 to 0.600. Any gasoline of either high or low using toluene diisocyanate only the amine component from octane value or high or low volatility can be characterized which the urea was formed is given in the table. It is underby its kinematic viscosity in centistokes at 77 F. readily 3O stood that the substituted urea additive was prepared by determinable by known methods. An increase in the visreacting two moles of the amine with one mole of the cosity of such a gasoline in the order of 10 up to 200% toluene diisocyanate.

TABLE I.KINEMATIC VISCOSITY 0F PREMIUM GASOLINE CONTAINING SUBSTITUTED UREA FORMED BY REAOTING TOLUENE DIISOCYANATE WITH THE INDICATED AMINE Average Percent Kinematic Increase in Run Amine component of substituted urea mol. wt. of substituted viscosity, cs. viscosity at amine urea in at 77 F. 77 F., gasoline Percent 1 None 0.557 2.. n-C alkyl primary beta amine 140 0. 05 O. 913 64 3-- o 140 0.10 0.300 149 4 n-Cu alkyl primary beta amine 170 0.05 0. 977 75 5 o 170 0.10 1. 08 255 6 010-14 secondary alkyl primary amine. 183 0. 10 0. 976 72 7-- o 183 0. 20 1.40 151 8..-. 2-ethylhexylamine 120 0.10 0 681 22 9-... Tertiary 011-14 alkyl primary amine" 200 0.05 0. 559 0. 3 10 Tertiary G g-24 alkyl primary amine 300 0.05 0. 560 0.5

due to the addition of an oil-soluble substituted urea of Runs 2 through 7 illustrate the invention and show a this invention will produce substantial economies in the premium gasoline of increased viscosity due to the addition operation of a spark-ignited, internal combustion engine. of the specific substituted ureas to produce a fuel providing The motor fuel of this invention can be prepared by adsubstantial fuel economies when employed in a car opermixing a suitable amount of the selected oil'soluble subated under level road conditions. In contrast, the ureas stituted urea directly into the gasoline. Alternatively, the formed using primary alkyl amines as shown in Runs S substituted urea can be formed in situ, that is, by adding through 10 were essentially ineffective for increasing the the components toluene diisocyanate and the amine sepaviscosity of the gasoline. rately to the gasoline wherein they will react to form a Engine tests were conducted in an RDH engine manusubstituted urea corresponding to the formula noted above. factured by Waukesha Motor Company. This 41.4 cubic It is understood that the motor fuel of the invention can inch displacement engine had a 9:1 compression ratio. also contain the additives conventionally employed in The engine was operated at 1200 r.p.m. or a 30 m.p.h. gasoline, such as alkyllead octane appreciators, alkyl hal- Level Road Load. The base fuel employed was the preide lead scavengers, anti-icing additives, corrosion inhibmium gasoline described above. The additive containing itors, dyes and the like. fuel contained the indicated amounts of the substituted As an example of the fuel economies that can be realized urea formed from the reaction of one mole of toluene by increasing the viscosity of a gasoline, it has been obdiisocyanate and two moles of secondary alkyl primary served that a base motor fuel having a Research Octane amine (Armeen L-9) having an average molecular Number 99.4 and a kinematic viscosity of 0.928 centistokes weight of 170 and an average of 11 chain carbon atoms. at 0 F., which has had its viscosity increased to 1.196 cen- The tests results are given in Table H below.

TABLE II Percent Viscosity Fuel/ Fuel con- Percent de- Hydro- Run Fuel substiincrease, air ratio sumption, crease in carbon tutcd urea Percent lbs/hr. iuel emission consmnp- (NDIR) tion p.p.m.

11 Base fuel 0.0943 2. 275 425 12 Additive fuel 0.10 0.0813 2.01 11.8 307 tistokes or by about 29% by the addition of a viscosity Additive fuels containing 0.20 and 0.25 weight permodifier when tested in a standard 1961 automobile encent of the same substituted urea in the above engine test gave comparable improvement in fuel consumption and substantially higher reduction in hydrocarbon emissions than the 28% reduction in Run 12 above.

Obviously many modifications and variations of the invention, as hereinafter set forth, may be made without departing from the spirit and scope thereof, and therefore, only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. A method of operating a spark-ignited internal combustion engine which comprises burning in said engine a motor fuel comprising a hydrocarbon mixture boiling in the gasoline boiling range containing an oil-soluble substituted urea, having the formula:

in which R and R are each alkyl radicals having from 1 to 18 carbon atoms and the sum of the carbon atoms in said R and R radicals collectively is at least 12, in an amount effective to increase the viscosity of said motor fuel measured as kinematic viscosity in centistokes by at least percent to 200 percent over the viscosity of said hydrocarbon mixture.

2. A method according to claim 1 in which the viscosity of said motor fuel is increased by an amount from about 40 to 100 percent.

3. A method according to claim 1 in which said motor fuel contains from about 0.005 to 0.5 Weight percent of said substituted urea.

4. A method according to claim 1 in which said substituted urea is the reaction product of 1 mole of toluene diisocyanate and 2 moles of n-C alkyl primary beta amine.

5. A method according to claim 1 in which said substituted urea is the reaction product of 1 mole of toluene diisocyanate and 2 moles of n-C alkyl primary beta amine.

6. A method according to claim 1 in which said substituted urea is the reaction product of 1 mole of toluene diisocyanate and 2 moles of C secondary alkyl primary amine.

7. A mot-or fuel composition comprising a hydrocarbon mixture boiling in the gasoline boiling range containing an oil-soluble substituted urea having the formula:

in which R and R are each alkyl radicals having from 1 to 18 carbon atoms and the sum of the carbon atoms in said R and R radicals collectively is at least 12, in an amount elfective to increase the viscosity of said motor fuel, measured as kinematic viscosity in centistokes by at least 10 percent to 200 percent over the viscosity of said hydrocarbon mixture.

8. A composition according to claim 7 in which the viscosity of said motor fuel is increased by an amount from about 40 to percent.

9. A composition according to claim 7 in which said motor fuel contains from about 0.005 to 0.5 weight percent of said substituted urea.

10. A composition according to claim 7 in which said substituted urea is the reaction product of one mole of toluene diisocyanate and 2 moles of n-Cg alkyl primary beta amine.

11. A composition according to claim 7 in which said substituted urea is the reaction product of 1 mole of toluene diisocyanate and 2 moles of n-C alkyl primary beta amine.

12. A composition according to claim 7 in which said substituted urea is the reaction product of 1 mole of toluene diisocyanate and 2 moles of C1044 secondary alkyl primary amine.

References Cited UNITED STATES PATENTS 3/1963 McCarthy et al. 25251.5 1/ 1965 Reuter et al. 4466 XR 

